Alzheimer's disease (AD) is a progressive degenerative disease of the brain primarily associated with aging. Prevalence of AD in the United States in 2000 was close to 4.5 Million. It was estimated that about one in ten individuals over 65 and nearly half of those over 85 are affected by Alzheimer's disease. Approximately 360,000 patients will be diagnosed with AD each year in the United States alone.
Clinical presentation of AD is characterized by loss of memory, cognition, reasoning, judgment, and orientation. As the disease progresses, motor, sensory, and linguistic abilities are also affected until there is global impairment of multiple cognitive functions. These cognitive losses occur gradually, but typically lead to severe impairment and eventual death in the range of four to twelve years.
Alzheimer's disease is characterized by two major pathologic observations in the brain: neurofibrillary tangles and beta amyloid (or neuritic) plaques, comprised predominantly of an aggregate of a peptide fragment know as Aβ. Individuals with AD exhibit characteristic beta-amyloid deposits in the brain (beta amyloid plaques) and in cerebral blood vessels (beta amyloid angiopathy) as well as neurofibrillary tangles. Neurofibrillary tangles occur not only in Alzheimer's disease but also in other dementia-inducing disorders.
3-amino-1-propanesulfonic acid (3APS, Tramiprosate, Alzhemed™) is a promising investigational product candidate for the treatment of Alzheimer's disease that is currently in Phase III clinical trials in North America and Europe (Wright, T. M., Drugs of Today (2006), 42(5): 291-298). This product is developed by Neurochem Inc. (Laval, QC, Canada) and it is believed to act by reducing the deposition and/or load of amyloid in the brain through its binding to soluble Aβ peptide. For increasing the therapeutic effectiveness of 3APS, it would be desirable to increase bioavailability, stability and/or crossing the blood brain barrier of 3APS. These and other needs can be satisfied by the disclosure herein of a prodrug form of 3-amino-1-propanesulfonic acid (3APS), pharmaceutical compositions and uses thereof to treat various medical disorders.
Previous metabolic stability studies had demonstrated that there was no in vitro metabolism of 3APS. Those studies include: 3APS metabolic stability in pooled human hepatocytes, human, rat and dog liver microsomes, human intestinal microflora, pooled human liver cytosol, and human arylamine N-acetyltransferase (See Examples 4 and 5).